The present invention relates generally to an internal combustion wave rotor employing detonative combustion for use as a direct thrust device.
Combustion engines offering superior performance, especially high levels of thrust, are highly desirable for use in flight vehicle propulsion. In particular great demand exists for combustion engines suitable for accelerating a vehicle to hypersonic speeds. Many useful missions exist for air-breathing hypersonic propulsion requiring efficiency over a wide range of Mach numbers (0-8). It is highly desirable that the engine retain propulsive thrust both at hypersonic speeds and at lower speeds useful for takeoff so that the engine may be used both to initiate flight as well as maintain flight and cruising speeds. It is further desirable to achieve these results utilizing combustion which does not require high-frequency ignition, complex valving arrangements, cyclically loaded moving parts, and nonsteady inlet and jet-nozzle flows. Minimizing NOx emissions is also desirable.
The present invention addresses these concerns by providing an intermittent-combustion detonation engine without the need for high frequency pulsed ignition. The invention further eliminates the use of moving parts that transmit load for better durability and reduced engine vibration. The invention also eliminates specialized valving to create varying air-fuel mixtures for purging, firing, and igniting the combustion chamber. The present invention also minimizes losses and noise due to non-steady flow in the propulsive fluid flows outside the combustion chamber. Accordingly, this invention results in a flight propulsion engine with many desirable superior features including: essentially steady, low-loss inlet and nozzle flows; high frequency operation without pulsed ignition; and no moving parts that transmit thrust.
A wave rotor detonation engine is provided to create motive thrust without the need for a compressed air source or a downstream turbine. The wave rotor detonation engine is an on-rotor combustion device where the combustion process occurs within the combustion chambers of the rotor.
To generate sufficient thrust, the wave rotor detonation engine creates detonative combustion within the channels of the rotor. The wave rotor detonation engine includes a housing, one or more inlet ports in the housing, one or more exhaust ports in the housing, a rotor rotatably mounted within the housing, one or more igniters, and a motor for rotating the rotor. The rotor includes a plurality of combustion chambers in which detonative combustion occurs. The combustion chambers extend longitudinally relative to the rotational axis of the rotor. Each combustion chamber has an inlet end for communication with the inlet port and has an outlet end for communication with the exhaust port.
To promote the creation of detonative combustion, a plurality of separate inlet zones may be provided for supplying fuel and air mixtures to the inlet end of the rotor. The inlet zones are circumferentially spaced about the perimeter of the rotor so that the combustion chambers interact with these inlet zones sequentially. A fuel injector is provided in selected inlet zones for injecting fuel into each respective zone. Each inlet zone is capable of introducing a different combustible mixture sequentially into a given combustion chamber as the chamber rotates past the respective inlet zone. For example, a first inlet zone may be provided for providing an input of air, without fuel, into the chamber. As the chamber in the rotor moves into registry with a second inlet zone, a fuel or fuel mixture may be input into the chamber. Additional inlet zones may be provided for successively inputting additional fuel or fuel mixtures which may be different from other fuels or fuel concentrations, into the chamber. Another inlet zone, such as the last inlet zone, may input a combustion enhancer or a mixture of fuel and the combustion enhancer into the combustion chamber proximal to the source of ignition to enhance detonative combustion. Using successive inlet zones results in the stratification of differing concentrations of combustible material within the combustion chambers.
For purpose of inputting a combustion enhancer into the combustion chamber, an enhancement injector for injecting a combustion enhancer into the respective combustion chamber is provided. Preferably, a combustion enhancer such as an oxidant is used in the inlet zone proximate to the igniter. After ignition, the combustion materials may be exhausted from the combustion chamber through the exhaust port. The chamber is successively charged, as desired, to have a mixture highly susceptible to initiation of detonative combustion.
In the alternate configuration, as shown in FIG. 5, having two inlet ports 32 and two exhaust ports 34, each port subtends a circumferential extent of about 90 degrees , and each inlet port 32 and paired exhaust port 34 is circumferentially offset from one another by about 45 degrees. Additional configurations having more inlet and exhaust ports and having the same relative proportions and locations are possible. In an alternate configuration, as shown in FIG. 8, the wave rotor detonation engine 10 may have one exhaust port 34 which subtends a full annulus of 360 degrees (the exhaust port 34 is in simultaneous communication with all of the combustion chambers 12) and may have one or more inlet ports 32 that subtend a total combined circumferential extent of about 240 degrees thereby communicating with about two-thirds of the combustion chambers 12.
The length of the rotor channels, the circumferential width of the inlet and exhaust ports, the placement of the exhaust port relative to the input port, and the rotational speed of the rotor are designed to control the cyclic flow processes, wave processes, and combustion processes to support detonative combustion within the wave rotor detonation engine. A CPU or electronic control system is optionally provided to control the rates of the rotor rotation, fuel injection, and ignition.